Myasthenia Gravis

How old should child be to have a thymectomy?

09/09/2009

Question:

I have heard of some children (8-12 yr olds) having thymectomy and symptoms of MG being reduced. I have also heard that the thymus gland is important for childrens immune system. My 6yr old daughter has recently been diagnosed with MG. She has the droopy eye, wondering eye, her smile has changed, complains of pain in her legs, constantly feels the need to stretch. Her last antibody test came back high - I am not sure what that means. Is she too young for a thymectomy? Where can I find the latest research about thymectomy for children?

Answer:

Most adult studies do not take the thymus out if the patient is younger than puberty, the time when the thymus is largest and then begins to involute. I have a very limited experience with thymectomy in youth and have followed only one young man with thymectomy before the age of 30 (he was 16 and had already started puberty and completed most of it).

We do not know the long term effects of removal of the thymus in childhood before puberty and the effects in adulthood on the immune system. I think of the thymus as the immune system high school, where white blood cells go to grow up and mature. Studies of children with thymectomy for other reasons (cardiac transplant and open heart surgery) have shown reduced white blood cell types later in life with signs of maturation of the T cells outside of the thymus. The question remains, do we decrease our immune response capacity by removing the thymus before puberty? More studies are needed. There will be risks associated with this because of the unknown, that must be balanced against the response rate. I would argue that it should only be considered for severe cases and major symptoms (respiratory weakness, marked swallowing problems, marked weakness), where traditional therapies have failed, rather than minor symptoms.

I have found papers that have reviewed children who have had thymectomy for myasthenia. Typically, the follow up is short and the long term immune system effects are not gauged. Of note, this was just reviewed in a paper from Children's Memorial Hospital at Northwestern in Chicago. They showed 31% remission, and 62% had improvement with thymectomy. They only had 13 patients in the review, and the average age was 10 years.

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